Our group has detected three potentially interesting cell surface antigens which appear to be tumor-associated. The antigens were initially detected on human melanoma using specific monoclonal antibodies. Extensive testing has shown that one of the antigens (3.1) has an extremely restricted distribution. The chemical nature of this antigen has not as yet been determined. The other two melanoma-associated antigens are proteins with molecular weights of approximately 97,000 (p97) and 210,000 (p210), respectively. These two protein antigens have similar types of distribution in that each is present in many of the melanoma cell lines and in some of the non-melanoma tumor cell lines tested, but not in any of the normal cell lines tested. Many normal adult human tissues have been examined for the presence of p97 and p210 and to date neither protein has been detected in these preparations. Both p97 and p210 are now being purified by immunoadsorption procedures using monoclonal antibodies. We propose to determine the chemical and structural natures of the purified antigens. Radioimmunoassays will be developed in order to quickly screen for these antigens in normal and malignant tissues as well as in sera from cancer patients.